1. Field of the Invention
The present invention relates to an exchange control system using a multi-processor.
2. Description of the Related Art
FIG. 13 is a block diagram illustrating an arrangement of a conventional exchange system including a control system. The conventional exchange system includes terminals 1-1 to 1-m which are connected through line interfaces 2-1 to 2-m to a main switch 3. Also included in the exchange system are trunk lines 5-1 to 5-p which are connected through line interfaces 4-1 to 4-p to the main switch 3. For the control of the terminals, the line interfaces 2-1 to 2-m-2 are connected to a main processor 11 through a bus 6, a sub-processor 7 and a bus 10, while the line interfaces 2-m-1 and 2-m as well as the line interfaces 4-1 to 4-p are connected to the main processor 11 through a bus 8, a sub-processor 9 and the bus 10.
Such a conventional exchange system is arranged so that the processors for setting the lines are previously fixedly determined. That is, line setting-signals input from the respective lines are fixedly transmitted to subprocessors 7 and 9 through the buses 6 and 8 respectively.
Accordingly, when the loads of the respective lines are unbalanced, it was necessary to previously allocate the sub-processors 7 and 9 according to the unbalanced loads.
Further, when the number of lines is increased, it was necessary for a manager of the system to know a subprocessor having an extra capacity and to physically change the system configuration in such a manner that the line setting signal is directed to the extra-capacity sub-processor. This means that the physical positions of the lines could not be freely determined but the positions of the connectable lines were determined by the situations of the processor.
For this reason, the conventional exchange system had the following problems in the case where each user terminal such as a telephone set is fixedly connected to the respective line, a load imposed on the processor caused by setting lines is determined by the number of lines. Accordingly, even when there is the above-described physical restriction in the system, there may be a possibility that the line load is balanced with the physical restriction to some extent. However, in the case where the lines are connected with branch type terminals such as a private branch exchange (PBX), the physical number of lines becomes unbalanced with the line setting load imposed on the lines. As a result, when there is such physical restriction to the processor, it becomes impossible to efficiently form exchange systems.
With the recent technological innovation in optical fiber or the like, the band width of lines has been greatly expanded and a single wide-band physical line is frequently being used as a plurality of physical lines based on time multiplexing or statistical multiplexing. As a result, it is expected that the unbalance between the number of the physical lines and the line setting load becomes a big problem.
In particular, when an asynchronous transmission mode (ATM) system, which has been recently developed by CCITT, an international standard organization, is employed, a transmission line of wide-band communication is logically multiplexed based on statistical multiplexing so that the band to be used for each logical line can be flexibly set. For this reason, it is virtually impossible to predict to what extent line setting signals are generated in the physical line. Accordingly, in the aforementioned system which fixedly allocates the line to the processor, it is difficult to properly allocate the processor processing resource.
Further, the exchange system having such arrangements, wherein data in the system are always controlled centrally by a single central processor, has another problem. That is, under the current situations in which the line setting load is increasing, the load imposed on the central processor becomes very high, thus requiring the processor to have a very high ability.
As has been explained in the foregoing, the control system of the conventional exchange system has been defective in that, since loads to be imposed on the line processor are previously set and used, when it is desired to expand or reduce the system, the system maintenance operator must consider the physical positions of the lines and therefore the physical position of a line to be physically connected (added) is restricted depending on the system applications.
In addition, that the bandwidth of the physical lines will become wider in the future and each of the lines will be flexibly used as logically multiplexed based on statistical multiplexing. Since loads cannot be restricted corresponding to the respective lines, the conventional structure for physically allocating the processing resources has a problem that a processor having a very high ability must be prepared for each line, thus resulting in an expensive system.